Reorder UpdateStatement, tighten comment, and cover empty-orders path

Three follow-ups from the review of #2781:

- Reorder visit_Arel_Nodes_UpdateStatement to sit between
  split_order_string and visit_Arel_Nodes_HomogeneousIn in
  oracle_common.rb. Groups the ORDER BY handling (order_hacks +
  split_order_string + UpdateStatement) together and keeps the
  IN-list cluster (HomogeneousIn + In + NotIn) intact.

- Rewrite the comment to make explicit that this override only
  handles the ORDER BY part. With a LIMIT, the statement is passed
  through to super so Oracle's own error for the unsupported
  LIMIT-in-UPDATE surfaces (the visitor does not try to smooth
  that over).

- Add a fifth visitor-level spec example covering the no-orders
  short-circuit (`return` from the if guard) — previously implicit
  via sibling tests that did not set orders.

Refs #2663 (task B).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: yahonda

lib/arel/visitors/oracle_common.rb

@@ -98,6 +98,18 @@ def split_order_string(string)
           array
         end
 
+        # Oracle does not allow ORDER BY in UPDATE statements. Strip it
+        # when no LIMIT is present; with a LIMIT, pass through so super
+        # surfaces Oracle's own error (LIMIT in UPDATE is unsupported too).
+        def visit_Arel_Nodes_UpdateStatement(o, collector)
+          if o.orders.any? && o.limit.nil?
+            o = o.dup
+            o.orders = []
+          end
+
+          super
+        end
+
         # To avoid ORA-01795: maximum number of expressions in a list is 1000
         # tell ActiveRecord to limit us to 1000 ids at a time
         def visit_Arel_Nodes_HomogeneousIn(o, collector)
@@ -145,18 +157,6 @@ def visit_Arel_Nodes_HomogeneousIn(o, collector)
           collector
         end
 
-        def visit_Arel_Nodes_UpdateStatement(o, collector)
-          # Oracle does not allow ORDER BY/LIMIT in UPDATEs.
-          if o.orders.any? && o.limit.nil?
-            # However, there is no harm in silently eating the ORDER BY clause if no LIMIT has been provided,
-            # otherwise let the user deal with the error
-            o = o.dup
-            o.orders = []
-          end
-
-          super
-        end
-
         def visit_Arel_Nodes_In(o, collector)
           attr, values = o.left, o.right
           return super unless values.is_a?(Array)

spec/active_record/connection_adapters/oracle_enhanced/arel/update_statement_spec.rb

@@ -48,4 +48,11 @@ def build_update(orders: [], limit: nil)
     sql = compile(stmt, visitor: oracle)
     expect(sql).not_to match(/ORDER BY/i)
   end
+
+  it "is a no-op when the statement has no orders" do
+    stmt = build_update
+    sql = compile(stmt)
+    expect(sql).not_to match(/ORDER BY/i)
+    expect(stmt.orders).to eq([])
+  end
 end